1. Technical Field
The present invention relates to tools for road construction, and more particularly to a road planing tool, which has its tool holder and replaceable tool bit combined by means of a joint mechanism for strengthening combination between the tool bit and the tool holder.
2. Description of Related Art
As shown in FIG. 1 and FIG. 2, an existing road planing tool comprises a tool holder 1 having an assembling socket 2. The assembling socket 2 is a round recess for receiving a generally cone-like tool bit 3 that is typically made of a hardened material such as tungsten steel. After the tool bit 3 is inlaid into the assembling socket 2, weld is applied to fixedly combine the tool bit 3 with the tool holder 1.
In road planing operation, the tool bit 3 of the road planing tool contacts the road surface for scraping off the asphalt road surface. Generally, such road planing tools are consumables, and would have the tool bit 3 worn out within two days under normal use, and even within 10 hours under heavy workload. Therefore, only the tool bit 3 is made of costly hardened material, and the tool holder is made of normal steel.
In the existing technology, there is no special combining structure between the tool bit 3 and the tool holder 1. Merely weld is applied to the boundary between the bottom of the tool bit 3 and the assembling socket 2. However, since the pressure is focused on the tool bit 3 during road planing operation, if the weld implemented is defective, the tool bit 3 is likely to come off the tool holder 1. A road planing machine typically has more than one hundred tools. In the event that the tool bit 3 escapes during road planing operation, the operation has to be broken off for replacing the tool, thus causing waste of time. In addition, once the tool bit 3 escapes, the tool is unusable, so the service life of the tool is significantly shortened and this increases costs.